Technical Field
The present invention relates to an image processing apparatus, image processing method, and image processing program for extracting an insertion route of an endoscope into a tube of a body, such as a tubular structure composed of a trachea and bronchi, using a three-dimensional image.
Background Art
Recently, image-based diagnosis has been performed widely in the medical front and an affected area is diagnosed using three-dimensional image data (volume image data) of a subject captured, for example, by an X-ray computed tomography (CT) system. For example, a three-dimensional image of a tubular structure composed of a trachea and bronchi may be generated by performing volume rendering on the volume data obtained by imaging a chest region. The three-dimensional image of the tubular structure is used to three-dimensionally identify the position of an abnormal region suspicious of, for example, lung cancer, and a bronchial endoscope is inserted to the position of the abnormal region to observe or treat the abnormal region, or otherwise various procedures are performed, such as collecting a tissue sample using, for example, biopsy forceps.
But, it is not easy to lead the distal end of an endoscope through a tube branched in multiple stages like a bronchus to an abnormal region located close to the end of the bronchus. Therefore, before inserting the endoscope into a tubular structure composed of a trachea and bronchi, it is preferable that the position of the abnormal region is confirmed, then a target point where a distal end portion of the endoscope should be located for performing a desired access to the abnormal region is set, and a route to the target point is set in advance based on a three-dimensional image of the tubular structure. To support the determination of such an endoscope route, a method is proposed in which a three-dimensional image of bronchi is generated based on volume data and a route from the lower respiratory tract to the target region along a tube is extracted on the three-dimensional image as described, for example, in Japanese Unexamined Patent Publication No. 2009-056143 and PCT Japanese Publication No. 2009-511155.
Further, as a guide to determine a route for a bronchoscope to safely reach the affected area, a technique is proposed in which a score is calculated for each region of bronchi based on various aspects, including route length, respiratory tract diameter, joint angle between respiratory tracts as described, for example, in PCT Japanese Publication No. 2009-542374.